This invention relates to a structure for use in an internal combustion engine for providing shortened vibration channels through which vibratory forces within engine cylinders are transmitted to a knock sensor attached to the engine at an exterior location.
It is the common practice to improve fuel economy in an internal combustion engine by advancing the spark of the engine as close to a value above which knocking occurs as possible and retarding the spark immediately when knocking occurs. For this purpose, spark control circuits have been proposed which can advance and retard the spark of an engine in response to the frequency of occurrence of engine knock. Such a spark control circuit includes a knock sensor attached to an engine at an exterior location where vibratory forces within the engine are translated into voltage signals at the knock sensor output. The spark control circuit also includes a pulse generator connected to the knock sensor for generating pulses to a counter while the knock sensor output is greater than the signal of background vibration produced by normal engine operation without knocking. The count of the counter corresponds to the frequency of occurrence of engine knock.
However, there has been recognized a serious problem in that the location for attachment of the knock sensor to the engine is spaced apart from the engine cylinders so that the vibratory forces produced within the cylinders are attenuated before conducting to the knock sensor.